Method for lightening petroleum hydrocarbon oil by distillation

ABSTRACT

A method for lightening a petroleum hydrocarbon oil by distillation in which 1 part by weight or less of an organic compound having an active mercapto group therein is added to 100 parts by weight of the petroleum hydrocarbon oil when the petroleum hydrocarbon oil is lightened by a thermal treatment.

TECHNICAL FIELD

The present invention relates to lightening a petroleum hydrocarbon oilby purifying the same by a thermal treatment operation to producematerials useful in the fields of, for example, fuels. Morespecifically, it relates to a method for obtaining light fractionsuseful for fuels and the like by previously adding an organic compoundhaving an active mercapto group therein to the petroleum hydrocarbonoil, followed by a thermal treatment, when the petroleum hydrocarbon oilis fractionated into each useful fraction by a distillation operation.

PRIOR ART

Heretofore, thermal cracking methods, catalytic cracking methods, andhydrogenating cracking methods have been used as methods for lighteningpetroleum hydrocarbon oils to produce materials useful in the fields of,for example, fuels and the like. In these methods, although hydrocarbonoils can be cracked at a high temperature by a thermal treatment toproduce useful light fractions, polymerization reactions occur,simultaneously with the thermal cracking reactions, and polymerizedheavy hydrocarbon compounds having a high molecular weight are obtainedas by-products. Various proposals have been made for obtaining usefullight fractions at a high yield by adding various additives to improvethe yield of the light fractions in the above-mentioned methods, asfollows:

(i) Methods of adding, as a thermal cracking radical stabilizer, forexample, dialkyl thiocarbomic acids, diaryl thiocarbomic acids, etc., ororganic phosphate esters, benzothiazoles etc., to petroleum heavy oils(see, for example, Japanese Unexamined Patent Publication (Kokai) No.57-90093); and

(ii) Methods of adding quinoline, tetrahydroquinoline, or a mixturethereof (see, for example, Japanese Unexamined Patent Publication(Kokai) No. 57-21487).

Nevertheless, a method for improving the lightening yield of a petroleumhydrocarbon oil only by a simple distillation operation has not beenproposed until now.

SUMMARY OF THE INVENTION

Accordingly, the objects of the present invention are to obviate theabove-mentioned problems in the state of the prior art and to provide amethod for obtaining light fractions useful in the fields of, forexample, fuels and the like, by an ordinary distillation operation notonly from heavy residual oils but also from crude oils, withoutdepending upon special catalytic and thermal cracking processes.

In accordance with the present invention, there is provided a method forlightening a petroleum hydrocarbon oil comprising the steps of: adding 1part by weight or less, preferably 0.001 to 0.1 part by weight, morepreferably 0.005 to 0.05 part by weight, of an organic compound havingan active mercapto group therein to 100 parts by weight of a petroleumhydrocarbon; and carrying out a distillation operation by a thermaltreatment.

BEST MODE OF CARRYING OUT THE INVENTION

The organic compounds having an active mercapto group therein usable inthe present invention are preferably those in a liquid state at anordinary temperature. Examples of such compounds are alkyl mercaptanssuch as octyl mercaptan, dodecyl mercaptan, dimercaptopropane, anddimercaptobutane; polyalkylene ether polythiols such as diethyleneglycoldimercaptane and triethylene glycol dimercaptan; esters ofthiocarboxylic acid with monohydric-to polyhydric-alcohols, such asisooctyl thioglycolate, 2-ethylhexyl mercapto propionate, ethyleneglycoldimercaptopropionate, butanediol dimercaptoacetate, trimethylolpropanetris-mercaptoacetate, and pentaerythritol tetrakis-3-mercaptopropionate.

The petroleum hydrocarbon oils capable of being lightened according tothe present method are not specifically limited. For example, variouscrude oils such as naphthenic crude oils, paraffinic crude oils, andmixtures thereof, as well as the topping residual oils and the vacuumdistillation residual oils thereof, can be lightened. Especially, thepresent method is preferably applied to petroleum hydrocarbon oils suchas crude oils having a low thermal history.

There are no specific limitations to distillation methods for lighteningpetroleum hydrocarbon oils according to the present invention and anyconventional distillation methods can be used when carrying out thepresent invention. Briefly, the preferable operation conditions arethose used by the conventional topping methods of crude oils except thatthe above-mentioned are added to the petroleum hydrocarbon oils at apreheating step before the distillation operation, to thoroughly mix theadditives with the petroleum hydrocarbon oils.

In the practice of the present invention, the yield of light fractionsuseful in the fields of, for example, fuels and the like, can beincreased in conventional distillation methods only by adding theabove-mentioned organic compounds having an active mercapto grouptherein to the petroleum hydrocarbon oils, without making the thermaltreatment conditions particularly severe.

The organic compounds having an active mercapto group therein to be usedin the present invention very readily react with unsaturated bonds andcause an addition reaction to double bonds at an ordinary temperature orupon slight heating, to saturate the same. Accordingly, when the organiccompound having an active mercapto group therein is added, variouscondensation polymerization reactions caused by radicals generatedduring the thermal treatment of petroleum hydrocarbon oils aresuppressed and the propagation or growth of unsaturated compounds to thegiant molecules is prevented.

EXAMPLE

The present invention will now be explained in detail with reference to,but is by no means limited to, the following Examples.

Example 1 (Distillation of Oman crude oil)

Fractionating tests of the crude oil were carried out by using adistillation apparatus according to ASTM-D2892. The fractionating testresults are shown in Table 1. Experiment No. 1 is a comparative test inwhich an organic compound having an active mercapto group therein wasnot added to the crude oil. In Experiment Nos. 2 and 3, 0.01 part byweight and 0.10 part by weight of pentaerythritoltetrakis-3-mercaptopropionate were added, as the organic compound havingan active mercapto group, to the crude oil, respectively. The crude oilused in the tests was Middle-East mixed crude oil mainly containing Omancrude oil.

                  TABLE 1                                                         ______________________________________                                        Experiment No.  1*         2      3                                           ______________________________________                                        Yield of 360° C.-fraction                                                              53.2       55.4   55.8                                        (wt %)                                                                        ______________________________________                                         *Comparative Experiment                                                  

As is clear from the results shown in Table 1, the economical value ofExperiment Nos. 2 and 3 according to the present invention is high whencompared to the comparative experiment, i.e., Experiment No. 1, becausethe difference of 2 to 3% by weight in the yields of the light fractionsis large, from the viewpoint of a large scale distillation treatment ofcrude oil.

Example 2 (Distillation of Topping Residual Oil)

Fractionating tests of topping residual oil were carried out by using adistillation apparatus according to ASTM-D 1160. The fractionating testresults are shown in Table 2. Experiment No. 1 was a Comparative test,in which an organic compound having an active mercapto group was notused. In Experiment Nos. 2 and 3, the fractionating tests were carriedout by adding trimethylolpropane tris-3-mercaptopropionate in an amountof 0.010 part by weight and 0.025 parts by weight, respectively, to thetopping residual oil. The topping residual oil used was 360° C.-fractionof topping residual oil of Middle-East mixed crude oil mainly containingKhafji crude oil.

                  TABLE 2                                                         ______________________________________                                        Experiment No.   1*        2      3                                           ______________________________________                                        360° C.-530° C. (Vol %)                                                          40.5      42.5   41.8                                        ______________________________________                                         *Comparative Example                                                     

As is clear from the results shown in Table 2, the increase of the yieldof the vacuum light oil of 1 to 2% by volume was obtained in the case ofExperiment Nos. 2 and 3, when compared to the Comparative Example (i.e.,Experiment No. 1). This increase in the yield is useful for holding thenecessary raw materials of the subsequent cracking process.

Example 3 (Distillation of Iranian Heavy Crude Oil)

The fractionating tests were carried out in the same manner as inExample 1, except that a crude oil mainly containing Iranian heavy crudeoil was used in lieu of the crude oil mainly containing Oman crude oil.

The results obtained are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Experiment No.      1*      2                                                 ______________________________________                                        Amount of additive added                                                                          None     0.015                                            (wt. part)                                                                    Yield of 350° C.-fraction                                                                  56.8    62.5                                              (Vol %)                                                                       ______________________________________                                         *Comparative Example                                                     

As shown in Tables 1 to 3, the yields of the light fractions wereincreased, when compared to each Comparative Example, by adding theorganic compound having an active mercapto group to the petroleumhydrocarbon oils according to the present invention, followed bycarrying out a conventional distillation operation.

I claim:
 1. A method of lightening a petroleum hydrocarbon oil bydistillation comprising adding 1 part by weight or less of at least onecompound selected from the group consisting of pentaerythritoltetrakis-3-mercaptoproprionate, trimethylolpropanetris-3-mercaptopropionate, pentaerythritol tetrakis-mercaptoacetate, andtrimethylolpropane tris-mercaptoacetate, to 100 parts by weight of thepetroleum hydrocarbon oil when the petroleum hydrocarbon oil islightened by a thermal treatment.
 2. A method as claimed in claim 1,wherein the petroleum hydrocarbon oil is a crude oil or topping residualoil.
 3. A method as claimed in claim 1, wherein the addition amount ofthe organic compound having an active mercapto group therein is 0.001 to1 part by weight, based on 100 parts by weight of the petroleumhydrocarbon oil.